Motor controller



April 19, 1932. c. T. EVANS 1,855,014

MOTOR CONTROLLER Original Filed April 22, 1921 I N V FN TOR.

A TTORNEY Patented Apr. 19, 1932 UNITED STATE.

RATENT OFFICE CLARENCE 'I. EVANS, OF MILXVAUKEE,

OF DELAWARE WISCONSIN, ASSIGNOB, BY MESNE ASSIGN- ZMENTS, TO CUTLER-HAMMER, IN-Zl, OF

"t-UKEE, VJISGONSIN, A CORPORATION lYIOTO'E- CONTROLLER Application filed April 22, 1921, Serial No. 571,762. Renewed January 8, 1923.

This invention relates to motor controllers although certain features thereof may be advantageously employed in other relations.

In practice there are numerous instances,

as for example in elevator service, where in order to obtain gradual acceleration of the motor driven apparatus and to protect the motor against excessive surges of current it is desirable to delay each step of acceleration for a given minimum time subject to an increase und-er abnormal current conditions. In other words, it is desirable to provide for both time limit and current limit control and the present invention has among its objects to provide an efiicient and reliable controller to so function.

Another object is to provide improved means to be employed in. motor controllers and other circuit controllers to afford time limit control and also current limit control if desired.

Another object is to provide control means having an inherently transient action due to variations in the current supplied thereto to afford time limit control said means also affording independent current limit control.

Other objects and advantages of the invention will hereinafter appear.

Certain embodiments of the invention are illustrated in the accompanying drawings and the same will now be described, it being understood that the embodiments illustrated are susceptible of various modifications without departing from the scope of the appended claims.

In the drawings,

Fig. 1 illustrates diagrammatically a controller employing a number of accelerating switches having individual means for timing the operation thereof;

Fig. 2 illustrates diagrammatically a modilied controller wherein the accelerating switches are controlled by a common timing instrumentality; and

Figs. 3 and 4: illustrate diagrammatically modified forms of timing instrumentalities.

Referring to Fig. 1, the same shows a controller for a direct current motor M of any preferred type which has been illustrated as comprising an armature a and series field This controller includes an electromagnetic main switch 1 to connect the motor across supply lines L and L2 through resistances it, 1 and R2, and electro-magnetic switches 2, 3 and 4 to respectively short-circuit said resistances.

The switches 1 to at are electrically interlocked as hereinafter more fully set forth to respond sequentially and the switches 2, 3 and i are respectively provided with relays 5, 6 and 7 to time the response thereof. Each of these relays as will appear afford both time limit and current limit control of its respective accelerating switch. Each relay normally occupies a position tending to render its respective accelerating switch responsire upon response of a preceding switch and as the relay must respond to delay response of its respective switch, it must be designed for relatively quicker response.

The relays are of like construction, each comprising a fixed contact 8 and a co-operating contact 9 which is carried by a magnetic member 10 pivotally mounted on a mag netic frame provided with windings l1 and 12. The magnetic frame provides a magnetic circuit for the winding 11 through the pivoted magnetic member 10 which serves as an armature and said frame is provided with a part 13 forming a magnetic shunt for said armature, said shunt preferably including a small air gap. The winding 12 which is short-circuited is mounted upon the part 13 of the magnetic frame and is thus placed in an inductive relation with respect to the winding 11. The armature 1O carries'a nonmagnetic adjusting screw 14; to engage a pole of the magnetic frame to maintain a predetermined air gap between said pole and armature upon attraction of the latter and said armature is biased by a spring 15 to normally engage contact 9 with contact 8, the spring being preferably adjustable to vary the sensitiveness of response of the relay.

The winding 11 of each relay as will hereinafter appear issubjected to the motor current and upon variation of the current traversing the same it induces a transient current in the Winding 12. The winding -12 when so excited acts to curtail the magnetic flux of winding 11 which traverses the path shunting the armature thereby increasing the magnetic pull on the armature and actually accelerating the pickup of the armature. Conversely when the current traversing the winding 11 becomes constant the winding 12 becomes ineffective thereby permitting an increase in the amount of magnetic flux shunted from the armature with a consequent decrease in the magnetic pull thereon. Thus it will be apparent that each relay may be readily designed and adjusted to respond at a given current value on a rising current and yet be released at a materially higher current value under constant current conditions.

The circuit connections shown in Fig. 1 are such that the winding 11 of each relay is included in the motor circuit only upon response of the switch preceding the switch controlled by such relay and as will be understood the motor current will tend to rise upon response of each of switches 1 to 4. Accordingly each relay when connected in circuit will have its winding 11 subjected to a rising current with the result of inducing transient current in its winding 12, the duration of the induced current being controlled by the rate and degree of variation in current supplied to winding 11. Thus each relay if made sufficiently sensitive may be caused to respond at least momentarily to provide a given minimum delay in response of the switch controlled thereby even though the motor current does not rise to a value rendering current limit control necessary. Moreover it will be apparent that if the motor current rises to a value exceeding the value at which any relay is designed and ad justed to release such relay will be retained in open position thus affording current limitcontrol in no wise limited as to duration by the transient action of its winding 12. As

.- will be understood the use of a plurality of relays is advantageous in that the same provide for timing response of the several switches independently of one another.

The power circuits shown in Fig. 1 may be traced as follows. Upon response of main switch 1, circuit is completed from line L through said switch by conductor 16 through winding 11 of relay by conductor 17 to and through resistances R, R and R2 in series by conductor 18 through the motor M to line L2. Upon response of the switch 2, circuit may be traced from conductor 16 by conductor 19 to and through switch 2 by conductor 20 to and through winding 11 of relay 6 to a point between resistances R and R thereby short-circuiting resistance R together with the winding 11 of relay 5. Upon response of switch 3 circuit may be traced from conductor 20 by conductor 21 to and through switch 3 by conductor 22 to and through the winding 11 of relay 7 to a point between resistances R and R2 thereby short-circuiting resistance R together with the winding 11 of relay 6. Upon response of switch 4 circuit is completed from conductor 22 by conductor 23 to and through switch 4 by conductor 24 to conductor 18 thereby shortcircuiting resistance R2 together with the winding 11 of relay 7 Thus as above stated, each of the relays is connected in circuit by the switch immediately preceding the switc 1 controlled thereby.

The control connections illustrated are similar to those of the ordinary series relay controller and may be briefly described as follows. The energizing circuit of main switch 1 is controlled by a manually operated switch 25 which when closed completes circuit from line L to and through the winding of switch 1 by conductor 26 to line L2. The energizing circuit of switch 2 is controlled by auxiliary contacts la of switch 1 which when engaged complete circuit from line L by conductor 27 through the contacts of relay 5 by conductor 28 to and through the winding of switch 2 by conductors 29 and 26 to line L2. The energizing circuit of switch 3 is similarly controlled by auxiliary contacts 2a of switch 2 and the contacts of relay 6 while the energizing circuit of switch 4 is similarly controlled by auxiliary contacts 360 of switch 3 and the contacts of relay 7 Thus, as above stated, the switches 1 to 4 are electrically interlocked to insure response thereof sequentially.

Referring to Fig. 2 the same illustrates a controller for direct current motor M, said controller comprising an electro-magnetic main switch 30 to connect the motor across lines L-L2 through resistances R, R and R2 as in Fig. 1 and electro-magnetic switches 31, and 33 to respectively short-circuit said resistances. In this instance the switches 30 to 33 are electrically interlocked in a slightly difierent manner to insure sequential operation thereof and the accelerating switches 31 to 33 are under the control of a common timing relay 34.

The relay 34 has a magnetic frame similar to that of the relays described but has two windings 35 and 36 to alternately induce currents in a short-circuited winding 37 mounted on that part of the magnetic frame shunting the armature. In this instance the frame has a small air gap in the circuit threading the several windings which air gap is located between and at right angles to the aXes of said windings. Also in this instance the armature is provided with a contact engageable with contacts 38, 39 and 40 for control of the accelerating switches 31 to 33.

The windings 35 and 36 of the relay 34 are wound in opposite directions and are connected in circuit alternately for successive responses of the relay. The circuit arrange ment'is such that upon closure of the main switch 1 the winding 35 is included in the motor circuit to cause the relay to act similarly to the relays above described to delay response of switch 31. Then upon response of switch 31 the winding 36 is included in the motor circuit, the windin 35 being shortcircuited together with resistance R. On the other hand response of accelerating switch 32 short-circuits winding 36 together with resistance R and reincludes in the motor circuit the winding 35, while response of switch 33 again short-circuits winding 35 together with resistance R2. Thus the relay is energized upon response of the switch preceding the switch controlled thereby and again energized upon response of its respective switch. Moreover due to the provision of oppositely wound coils and to the aforedescribed control thereof, the relay is subjected to current variations of considerably wider range than the simultaneous variations in motor current, for as will be observed when either winding is short-circuited and the other connected in circuit the winding 37 is subjected to the influence of the falling current in the former and the rising current in the latter.

The power connections of Fig. 2 may be traced as follows. Upon response of switch 30, circuit is completed from line L through said switch by conductor 41 through relay winding 35 by conductors 42 to and through the resistances R, R and R2 to and through the motor to line L2. Switch 31 upon response completes circuit from conductor 41 by conductor 43 to and through said switch by conductor 44 to and through the relay winding 36 by conductor 45 to a point between resistances R and R thereby shortcircuiting resistance R together with relay winding 35. Switch 32 upon responding completes circuit from conductor 41 to and through relay winding 35 by conductor 46 to and through said switch to a point between resistances R and R2 thereby shortcircuiting resistance R together with relay winding 36. Switch 33 upon responding completes circuit from line L to and through switches 30 and 31 to conductor 44 by conductor 47 to and through switch to a point between resistance R2 and the motor thereby short-circuiting resistance R2 together with relay winding 35.

The control circuits may be traced as follows. The energizing circuit of switch 30 extends from line L through a control switch 48 to and through the Winding of said switch 30 by conductor 49 to line L2. The energizing circuit of switch 31 is controlled by switch 30 and upon response of the latter switch may be traced from line L by conductor 50 through the relay 34 to contact 38 by conductor 51 through auxiliary contacts 30a of switch 30 by conductor 52 to and through the winding of switch 31 by conductors 53 and 49 to line L2. Switch 31 has auxiliary contacts 31a to establish a maintaining circuit for itself and auxiliary contacts 31?) to complete the energizing circuit of switch 32 from relay contact 39. The switch 32 has similar auxiliary contacts for establishing a maintaining circuit and for completing the circuit of switch 33 from relay contact 40 while switch 33 has auxiliary contacts 33a to establish its own maintaining circuit.

Referring to Figs. 3 and 4 the former shows a form of relay which may be substituted for that shown in Fig. 1 while Fig. 4 shows a relay whicu may be substituted for that shown in Fig. 2. Both relays have windings identical with the corresponding relays of Figs. 1 and 2 and their windings are therefore designated by the same reference numerals. The only difference between these relays and their corresponding relays of Figs. 1 and 2 resides in the magnetic frame construction. Whereas in Figs. 1 and 2 each relay has a unitary magnetic frame, the magnetic frames of Figs. 3 and 4 are divided whereby the flux of the winding 11, Fig. 3. is confined to a path treading the coil 12 while the fluxes of the windings 35 and 36, Fig. 4, are confined to a path threading the winding 37, the common portion of the magnetic frame being preferably provided with a small air gap. Accordingly in each case the attraction of the armature is dependent upon the flux of the short-circuited coil which in turn is dependent upon the transient currents induced in such coil. Accordin ly while these relays will function in a manner similar to their corresponding relays of Figs. 1 and 2 they will be dependent upon fluctuations of the motor current for current limit control. lVhen the motor current becomes constant regardless of the value thereof the relays will tend to release but by proper design and adjustment a substantial degree of current limit control may nevertheless be obtained.

It is of course to be understood that where current limit control is not required the relays shown may be employed purely for time liniit control being for this purpose provided with either series or shunt windings suitably controlled to induce transient currents in the short-circuited coils.

lvhat I claim as new and desire to secure by Letters Patent is:

1. In a controller for direct current motors, in combination, starting and accelerating means and a relay affording time limit control of said means, said relay havmg a winding to be subjected to a varying current for a temporary period only by a given operation of said means and having a short-circuited winding arranged in an inductive relation with respect to the former winding.

2. In a controller for rect current motors, in combination, starting and accelerating means and a time limit control instrumentality therefor comprising a magnetic frame including an armature member and windings arranged on said frame in an inductive relation, one of said windings being subjected to a varying current by a given operation of said means and the other of said windings being short-circuited whereby said armature is subjected to influence by the transient action of said short-circuited Winding due to the Varying current supplied to said first-mentioned winding.

3. In a controller for direct current motors, in combination, starting and accelerating means and a timing relay therefor comprising a winding to be subjected to a varying current by a given operation of said means, a short-circuited winding, an armature member and means aii'ording a mag netic circuit for certain of said windings which circuit includes said armature member and further aifording a magnetic circuit exclusive of said armature member which circuit threads both of said windings.

4. In a controller for direct current motors, in combination, starting and accelerating means, and a relay affording time limit and current limit control of said means, said relay having a Winding to be included in the motor circuit for a temporary period only and having a short-circuited winding arranged in an inductive relation with respect to the former windin 5. In a controller for direct current motors, in combination, starting and accelerating means and a time limit and current limit control instrumentality therefor having an operating winding to be included in the motor circuit and further having a shortcircuited control winding arranged in an inductive relation with respect to the former winding.

6. In a controller for direct current motors, in combination, starting and accelerating means and a time limit and current limit control instrumentality therefor having a winding to be connected in the motor circuit, a magnetic shunt for the flux of said winding and a short-circuited winding arranged in an inductive relation with respect to the former winding to control said magnetic shunt.

7. In a controller for direct current motors, in combination, starting and accelerating means and a time limit and current limit control instrumentality therefor comprising a magnetic frame including a movable armature member and magnetic shunt for the latter, a winding mounted on said frame to be subjected to the motor current for attraction of said armature member and a short-circuited winding arranged in an inductive relation with respect to the former 

